M&S says

This charming and effortlessly smart cable knit cardigan, made from soft, cotton rich fabric for a comfy feel all day, is the perfect partner to short sleeve school blouses or summer school dresses. A cute patterned knit lends a touch of style to school uniforms, and ribbed trim sleeves and waist give a neat and cosy fit. Coming in a range of colours to match any school's uniform, this cute school cardigan is complete with StayNEW™ technology to look bright and new for longer.